Going crazy with end-to-end soldering

[TigerhawkT3]

I've been trying to solder some AA NiMHs for a hotwire I'm planning, and it's not going well at all. I thought I was supposed to get flat tops, but my experience has shown me that flat top cells are HORRIBLE for soldering. The hammerhead tip is too wide and concave to touch the positive contact without melting the shrinkwrap, and then when I press the cells together, the solder just gets pushed to the outside, where it quickly shorts the cells. It's all the more frustrating because I thought I had all the proper equipment and was using the proper cells. Next time, I'll use button tops for sure, and hopefully I'll find a copper hammerhead tip that doesn't oxidize within minutes of turning on the iron, turning everything crusty and black. The one I have looks like garbage, and the ends have turned concave, which is pretty much the opposite of what you'd want.

I am so incredibly frustrated with all the time, money, effort, and burns I've been through with this cursed project.

 

[LuxLuthor]

LOL! I sense some frustration. I gave you the exact techniques in the videos linked in your other thread here.

I have done at least 100 welds of Titaniums and Elite 2/3A cells using that exact technique, and not ruined a single cell. Flat tops are the way to go for proper soldered contact and straight alignment. You must be using way too much solder to have a short. You must not be removing wrappers like the video shows, to be melting them.

It is true after a few minutes of using the HammerHead, you discover that a little dremel when its cool removes the outer plating cover so you have a conductive solder coated surface. Thereafter, the age old technique of wiping head surface on moist sponge to clean off excells solder works perfectly.

I use the 66/44 0.031" finer solder to tin battery ends after dremel abrasion. After I'm done with a 3, 4, 5, 6 stick length, I either shrink it in some 3mil or 1mil Kapton tape. All of that is shown in the video. I guarantee it works perfectly if you follow it.

Edit: Oh and I always flux the surfaces of abraded battery ends (I love HN's Superior liquid flux) before pre-tinning both ends of all cells I am going to use (even though this solder has flux core)....then just apply a fresh bit of solder to both sides of hammer before placing between terminal ends in battery jig. If your hammer head is too wide for your batteries, just dremel the POSITIVE end to make a bit smaller, but the one I got from CBP works perfectly for me.

You may be holding it on ends too long before sliding two batteries together. I place hammerhead on POSITIVE terminal of bottom battery, then quickly slide the upper battery down against top of iron, wait no more than 1/2 second--I count "One Thousa" (of "One Thousand one"), pull out iron and quickly slide top down to make joint. I probably wipe the heads of the hammerhead tip on sponge every 3rd solder, and apply fresh solder. Lightly abrade/clean the ends of hammerhead with dremel, and I think you will find your iron issues will go away.

PS.) I feel strange giving you advice after seeing your wonderful YouTube videos which taught me some things I had not been doing the best way. HN also has some nice tips on that link, but many other good sites with tips also. I tried his 60/40 solder, but really prefer this Kester 66/44/.031 flux core that I got with my Hakko 936 station.

 

[TigerhawkT3]

"Some frustration" is definitely an understatement.

After so much failure, I thought I might be using too much solder, but when I started using less, the welds didn't hold! The hammerhead, along with my pressing the cells firmly together, would just push all the solder to the edges, where it would melt through the insulation and cause shorts. This is probably one of those things where I needed to have someone next to me telling me what I did wrong.

If I removed the insulation, wouldn't the cells short as soon as I put them in the metal soldering jig? :thinking:

 

[macforsale]

*

 

[LuxLuthor]

"Some frustration" is definitely an understatement.

After so much failure, I thought I might be using too much solder, but when I started using less, the welds didn't hold! The hammerhead, along with my pressing the cells firmly together, would just push all the solder to the edges, where it would melt through the insulation and cause shorts. This is probably one of those things where I needed to have someone next to me telling me what I did wrong.

Did you abrade both ends, apply flux, and pre-tin battery ends with a very small amount?

The copper hammerhead is just plain copper. Once I heated it the first time and saw that solder was not covering it, I unplugged and VERY lightly abraded the outer copper surface. I speculated that they had some kind of protective coating that needed to be sanded off after the first heating discolored it.

Ever since that first time, I have had a nice coating of solder, and about every 3rd battery weld, I wipe both sides on sponge and reapply fresh solder. If you are having solder extrude onto the plastic wrapper and melting through, then you are using too much.

If you then went with too little solder, I'm guessing you still don't have a clean hammerhead with fresh, shiny solder on its ends, or you are taking too long to slide battery down...or not using flux or something.

Honestly, I have done at least 120 cells (I did another 16 cells today), and just don't have any problem....so there is something with your technique. All of mine are flat tops.

If I removed the insulation, wouldn't the cells short as soon as I put them in the metal soldering jig? :thinking:

Mine had a layer of durable, plastic clear coat on it, and I had added my own clear package tape to the inside jig surfaces just in case, and to slide easier. I guess I am assuming too many things here. This is exactly what they make these jigs and hammerhead for. If youi send an email to Mike who owns CheapBatteryPacks.com, he will tell you that this is exactly the iron setup that he uses for making soldered packs to order.

 

[TigerhawkT3]

I usually abrade the ends and pre-tin, but I don't have flux (well, besides the solder core).

I have no idea if there was a coat of some sort on the hammerhead. I would never have thought it had one if you hadn't mentioned it just now. I'll try taking a pic of my tip tomorrow so you can see what I've been working with.

Again, I have no idea if the jig has a clear coat on it. It might be that when one of the cells shorted and heated up, it melted through the coating. There is a weird streak/smudge on the jig that wasn't there when it was new, and I can't get it out. I'll try taking a pic of that, too.

I ragged on the flat tops because before doing those, I did some C NiMHs for my bike light, and those were fine. They have big button tops, and the cells themselves are also quite large.

Know what I should have done? I should have gotten a bulk package of cheapo CZn cells and practiced with those. But no, instead, I practiced with special-ordered $2/each cells. Clever me.

I already Gooped the pack and soldered on the battery bars (which was curiously easy, BTW), so I've got the pack done, and I'll probably just test it out tomorrow to see what happens (instaflash? Fire? Success?). I'll get a couple wires and my friend the electrical tape, and I'll pray.

 

[LuxLuthor]

It's all grist for the mill.